Busting the Lens dictates Focus Speed Myth

Started Mar 22, 2013 | Discussions thread
Steve Balcombe
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Re: Busting the Lens dictates Focus Speed Myth
In reply to meland, Mar 25, 2013

meland wrote:

3 The type of AF motor used in the lens - you get what you pay for. The latest USMs are usually faster than cheaper micro motors.
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5 The distance the lens elements have to be moved for any given focus point change. A lens like a 100mm macro can have several rotations of the focus ring to go from its closest focus distance to infinity. Focus limiters can help keep the focussing within a prescribed range and thus speed things up.

One complicating factor is that lower-cost lenses are designed as such from the ground up - you don't just take a high quality lens and stick a cheaper motor in it. So while they will typically have micromotor AF which is inherently slow, they will also be designed with a very short travel so they can get from (say) 5m to infinity in just a few degrees of rotation - which takes a fraction of a second.

But TANSTAAFL and the penalty is less accurate AF (but often perfectly acceptable in an f/4-5.6 lens) and much less satisfactory MF.

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